The invention is directed to thiazolidin-4-carbonitriles substituted in the 2-position and salts of such compounds and a process for their production. The thiazolidin-4-carbonitriles of the invention are substituted once or twice.
The thiazolidin-4-carbonitriles of the invention are particularly those which have the formula ##STR2## in which R.sub.1 and R.sub.2 are the same or different and individually are hydrogen or straight or branch chain alkyl or alkenyl groups with preferably up to 12 and particularly up to 4 carbon atoms, or are cycloalkyl or cycloalkenyl groups with preferably up to 6 carbon atoms or are aryl groups or aralkyl groups with up to 4, and especially up to 2 carbon atoms in each alkyl group with the proviso that not over one of R.sub.1 and R.sub.2 is hydrogen or R.sub.1 and R.sub.2 together with the adjacent ring carbon atoms form a ring, e.g., R.sub.1 and R.sub.2 together are an alkylene group of preferably 3 to 12 carbon atoms, and particularly 4 to 7 carbon atoms.
The alkyl groups include for example n-pentyl, n-hexyl, 2-ethylhexyl, n-octyl or n-dodecyl or especially methyl, ethyl, propyl, isopropyl, n-butyl, sec.butyl or tert.butyl; when R.sub.1 and R.sub.2 are joined together they form for example a trimethylene, tetramethylene, pentamethylene, hexamethylene or heptamethylene group; the alkenyl groups include for example hexen-(3)-yl-(1) or dodecen-(8)-yl-(1) or especially vinyl, allyl, methallyl or crotyl group; the cycloalkyl groups are for example cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl or cyclooctyl; the cycloalkenyl groups include for example cyclopropenyl, cyclopentenyl or cyclohexenyl; the aryl groups include for example phenyl or naphthyl; the aralkyl groups are for example phenylpropyl or especially benzyl or phenethyl; the alkaryl groups include for example 4-tert.-butylphenyl or especially p-tolyl, o-xylyl or 4-ethylphenyl.
Examples of the thiazolidin-4-carbonitriles within the invention include 2-methyl-thiazolidin-4-carbonitrile, 2,2-dimethyl-thiazolidin-4-carbonitrile, 2-ethyl-thiazolidin-4-carbonitrile, 2-methyl-2-ethyl-thiazolidin-4-carbonitrile, 2,2-diethyl-thiazolidin-4-carbonitrile, 2-methyl-2-n-propyl-thiazolidin-4-carbonitrile, 2-methyl-2-isopropyl-thiazolidin-4-carbonitrile, 2-phenyl-thiazolidin-4-carbonitrile, 2-o-xylyl-thiazolidin-4-carbonitrile, 2-cyclohexyl-thiazolidin-4-carbonitrile, 2,2-pentamethylene-thiazolidin-4-carbonitrile, 2-isopropyl-thiazolidin-4-carbonitrile, 2,2tetramethylene-thiazolidin- 4-carbonitrile, 2,2-hexamethylene-thiazolidin-4-carbonitrile, 2,2-heptamethylene-thiazolidin-4-carbonitrile, 2,2-undecamethylene-thiazolidin-4-carbonitrile, 2,2-diphenyl-thiazolidin-4-carbonitrile, 2-methyl-2-phenyl-thiazolidin-4-carbonitrile, 2-p-tolyl-thiazolidin-4-carbonitrile, 2-o-ethylphenyl-thiazolidin-4-carbonitrile, 2-p-butylphenyl-thiazolidin-4-carbonitrile, 2-benzyl-thiazolidin-4-carbonitrile, 2,2-dibenzyl-thiazolidin-4-carbonitrile, 2-methyl-2-benzyl-thiazolidin-4-carbonitrile, 2-phenethyl-thiazolidin-4-carbonitrile, 2-naphthyl-(1)-thiazolidin-4-carbonitrile, 2-cyclopentyl-thiazolidin-4-carbonitrile, 2-methyl-2-cyclopropyl-thiazolidin-4-carbonitrile, 2-cyclohexenyl-thiazolidin-4-carbonitrile, 2-n-butyl-thiazolidin-4-carbonitrile, 2,2-di-n-butyl-thiazolidin-4-carbonitrile, 2-methyl-2-n-butyl-thiazolidin-4-carbonitrile, 2-methyl-2-sec.butyl-thiazolidin-4-carbonitrile, 2-dodecyl-thiazolidin-4-carbonitrile, 2-ethyl-2-dodecyl-thiazolidin-4-carbonitrile, 2-methyl-2-octyl-thiazolidin-4-carbonitrile, 2-vinyl-thiazolidin-4-carbonitrile, 2-methyl-2-vinyl-thiazolidin-4-carbonitrile, 2-allyl-thiazolidin-4-carbonitrile, 2-ethyl-2-allyl-thiazolidin-4-carbonitrile, 2-crotyl-thiazolidin-4-carbonitrile and 2-methyl-2-methallyl-thiazolidin-4-carbonitrile.
The salts of the invention of the thiazolidin-4-carbonitriles substituted in the 2-position are addition salts of the nitrile with organic and especially inorganic acids. The organic acids include aliphatic, alicyclic, aromatic or heterocyclic mono or polycarboxylic acids or sulfonic acids as for example formic acid, acetic acid, propionic acid, butyric acid, valeric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, glycolic acid, tartaric acid, malic acid, maleic acid, fumaric acid, citric acid, ascorbic acid, hydroxy maleic acid, pyruvic acid, phenyl acetic acid, benzoic acid, p-anthranilic acid, p-hydroxybenzoic acid, salicylic acid, p-aminosalicylic acid, methanesulfonic acid, ethanesulfonic acid, hydroxyethanesulfonic acid, halobenzenesulfonic acid, e.g., p-chlorobenzenesulfonic acid, toluenesulfonic acid, e.g., p-toluenesulfonic acid, or sulfanilic acid. The inorganic acids are especially mineral acids and chiefly strong mineral acids, as for example sulfuric acid, phosphoric acid and hydrohalic acids, e.g., hydrochloric acid and hydrobromic acid. Particularly well crystallizing salts are the hydrochlorides.
The thiazolidin-4-carbonitriles substituted in the 2-position according to the invention are produced from the corresponding thiazoline-(3) compounds of the formula ##STR3##
Suitable thiazolines for example are 2-methyl-thiazoline-(3)-, 2,2-dimethyl-thiazoline-(3), 2-ethyl-thiazoline-(3), 2-methyl-2-ethyl-thiazoline-(3), 2,2-dimethyl-thiazoline-(3), 2-methyl-2-n-propyl-thiazoline-(3), 2-methyl-2-isopropyl-thiazoline-(3), 2-phenyl-thiazoline-(3), 2,2-hexamethylene-thiazoline-(3), 2-cyclohexyl-thiazoline-(3), 2,2-pentamethylene-thiazoline-(3), 2-isopropyl-thiazoline-(3), 2,2-tetramethylene-thiazoline-(3), 2,2-heptamethylene-thiazoline-(3), 2,2-undecamethylene-thiazoline-(3), 2,2-diphenyl-thiazoline-(3), 2-methyl-2-phenyl-thiazoline-(3), 2-p-tolyl-thiazoline-(3), 2-o-ethylphenyl-thiazoline-(3), 2-p-butylphenyl-thiazoline-(3), 2-benzyl-thiazoline-(3), 2,2-dibenzyl-thiazoline-(3), 2-methyl-2-benzyl-thiazoline-(3), 2-phenethyl-thiazoline-(3), 2-naphthyl-thiazoline-(3), 2-cyclopentyl-thiazoline-(3), 2-methyl-2-cyclopropyl-thiazoline-(3), 2-cyclohexenyl-thiazoline-(3), 2-methyl-2-cyclohexenyl-thiazolidine-(3), 2-n-butyl-thiazoline-(3), 2,2-di-n-butyl-thiazoline-(3), 2-methyl-2-n-butyl-thiazoline-(3), 2-methyl-2-sec.butyl-thiazoline-(3), 2-dodecyl-thiazoline-(3), 2-ethyl-2-dodecyl-thiazoline-( 3), 2-methyl-2-octyl-thiazoline-(3), o-xylyl-thiazoline-(3), 2-vinyl-thiazoline-(3), 2-methyl-2-vinyl-thiazoline-(3), 2-allyl-thiazoline-(3), 2-ethyl-2-allyl-thiazoline-(3), 2-crotyl-thiazoline-(3), 2-methyl-2-methallyl-thiazoline-(3).
These thiazolines can be prepared for example by reaction of mercaptoacetaldehyde with an oxo compound and ammonia (Asinger U.S. Pat. No. 2,879,273) or especially by reaction of (1) a halogenated acetaldehyde, e.g., chloroacetaldehyde with (2) an oxo compound, e.g., acetone, (3) a metal or ammonium hydrogen sulfide, e.g., sodium hydrogen sulfide and (4) ammonia (see Scherberich U.S. application Ser. No. 840,714 entitled "Process for the Production of Thiazoline-(3) Compounds" filed on even date and corresponding to German application No. P 26 45 731.8 filed Oct. 9, 1976). The entire disclosures of the Asinger patent and the Scherberich U.S. application are hereby incorporated by reference and are relied upon.
The thiazoline-(3) compound is reacted with hydrogen cyanide to form the thiazolidin-4-carbonitrile. The hydrogen cyanide is added as such in gaseous or liquid form or as a solution in water or an organic solvent or is produced directly from other compounds, for example by reacting an acid, e.g., hydrochloric acid or sulfuric acid with an alkali cyanide, e.g., sodium cyanide or potassium cyanide. There can be used substantially any proportions either stoichiometric or over or under stoichiometric amounts. Generally, it is suitable to employ at least 1 mole but not over about 10 moles of hydrogen cyanide per mole of thiazoline. Preferably there are used 1.1 to 1.5 moles of hydrogen cyanide per mole of thiazoline.
Although the reactants, i.e., the thiazoline-(3) and the hydrogen cyanide, can be used undiluted, it is advantageous to carry out the reaction in the presence of solvents such as water or inert organic liquids. As organic liquids there can be used for example alcohols, esters, ethers or aliphatic or aromatic hydrocarbons, or halogenated aliphatic or aromatic hydrocarbons. Examples of such inert organic liquids are methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, dimethyl ether, diethyl ether, dipropyl ether, dibutyl ether, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl butyrate, hexane, octane, petroleum ether, benzene, toluene, xylene, chloroform, carbon tetrachloride, dichloroethylene, methylene chloride and chlorobenzene.
The reaction temperature in a given case is adjusted according to the reactants and the solvent. Generally, temperatures from about -10.degree. to +250.degree. C. are chosen. Preferred are temperatures between about 0.degree. and 100.degree. C., particularly from 10.degree. to 50.degree. C.
The thiazolidin-4-carbonitrile is separated from the reaction mixture for example by cooling the mixture or by driving off the solvent which in a given case may be present.
The salts of the thiazolidin-4-carbonitriles are produced by treating the thiazolidin-4-carbonitrile, in a given case directly in the reaction mixture resulting from the production of the thiazolidin-4-carbonitrile, with the acid in question. The acids can be used in widely varying amounts at random, both in stoichiometric as well as under and over stoichiometric amounts. Generally, it is suitable to use at least 1 mole but not more than 5 moles of acid per mole of thiazolidin-4-carbonitrile. Preferably there are used 1.1 to 1.5 moles of acid per mole of thiazolidin-4-carbonitrile. Conversely the salts of thiazolidin-4-carbonitrile can be converted by means of bases, e.g., sodium hydroxide or anion exchangers into the free thiazolidin-4-carbonitrile.
The thiazolidin-4-carbonitriles substituted in the 2-position and in a given case their salts serve particularly as starting materials for the production of D,L-cysteine to which they can be converted by treatment with mineral acids, e.g., hydrochloric acid, preferably at elevated temperature. The formation of D,L-cysteine from the thiazolidin-4-carbonitrile is disclosed in more detail and claimed in Offermanns and Scherberich application Ser. No. 840,715 entitled "Process for the Production of D,L-Cysteine" filed on even date and corresponding to German application No. P 26 45 748.7 filed Oct. 9, 1976. The entire disclosure of the Offermanns et al. application is hereby incorporated by reference and relied upon.
In this manner there is produced a D,L-cysteine of outstanding quality and purity which can be used for example directly for fodder purposes. It has excellent stability and surprisingly does not change even upon long storage while cysteine produced in the customary way readily converts to cystine.
Unless otherwise indicated all parts and percentages are by weight.
The process can comprise, consist essentially of or consist of the steps set forth with the stated materials.